Fluoroaryl magnesium halide is a useful compound as a Grignard reagent used in various types of organic synthetic reactions, for example. Also, the fluoroaryl magnesium halide is a useful compound, for example, as an intermediate of a fluoroaryl borane derivative, used in manufacturing a cocatalyst which promotes an activity of a metallocene catalyst (polymerization catalyst) used in a cation complex polymerization reaction, or a catalyst for silicone photo-polymerization. Recently, the metallocene catalyst has been receiving considerable attention as a polyolefin polymerization catalyst.
Various proposals have been made as a method of synthesizing the fluoroaryl magnesium halide. For example, J. Chem. Soc., 166 (1959) discloses a method of synthesizing pentafluorophenyl magnesium bromide, which is a species compound of the fluoroaryl magnesium halide, by reacting bromopentafluorobenzene with magnesium using diethyl ether as a solvent.
Also, J. Organometal. Chem., 11, 619-622 (1968) and J. Organometal. Chem., 26, 153-156 (1971) disclose a method of synthesizing pentafluorophenyl magnesium halide, which is a species compound of the fluoroaryl magnesium halide, by a Grignard exchange reaction of fluoroaryl halide (chloropentafluorobenzene, bromopentafluorobenzene, and iodopentafluorobenzene) and ethyl magnesium halide using tetrahydrofuran (THF) as a solvent. Also, U.S. Pat. No. 5,693,261 discloses a method of synthesizing pentafluorophenyl magnesium halide by a Grignard exchange reaction of chloropentafluorobenzene and isopropyl magnesium halide.
On the other hand, Japanese Laid-open Patent Application No. 295985/1997 (Japanese Official Gazette, Tokukaihei No. 9-295985, published on Nov. 18, 1997) discloses a method of preparing fluoroaryl magnesium halide (Grignard reagent) by reacting fluoroaryl halide with magnesium using alkyl halide as a catalyst.
However, in the method of synthesizing pentafluorophenyl magnesium bromide disclosed in J. Chem. Soc., 166 (1959) supra, the synthesis pentafluorophenyl magnesium bromide is colored considerably with coloring components produced by the side reaction or the like. For this reason, when a fluoroaryl borane derivative is synthesized by using the pentafluorophenyl magnesium bromide as a Grignard reagent, a colored fluoroaryl borane derivative is produced as the final product unless the coloring components are removed.
The method for manufacturing pentafluorophenyl magnesium halide disclosed in J. Organometal. Chem., 11, 619-622 (1968) and J. Organometal. Chem., 26, 153-156 (1971) supra use THF as the solvent. However, the fluoroaryl borane derivative synthesized using a THF solution of the resulting pentafluorophenyl magnesium halide includes strong Lewis acids, for example. Thus, there is a problem that the resulting fluoroaryl borane derivatives trigger ring-opening polymerization of THF used as the solvent or causes a large amount of by-product to be produced.
Also, the method for manufacturing pentafluorophenyl magnesium halide disclosed in U.S. Pat. No. 5,693,261 supra has a problem that, because chloropentafluorobenzene has poor reactivity, chloropentafluorobenzene has to be used excessively with respect to isopropyl magnesium halide. Further, this method has another problem that it demands a step of removing the excessively used chloropentafluorobenzene from the final product (commercial goods).
The method of preparing the Grignard reagent disclosed in Japanese Laid-open Patent Application No. 295985/1997 supra has a problem that, although the coloring of the resulting Grignard reagent is slightly reduced if diethyl ether is used as the solvent (reaction solvent), the resulting Grignard reagent is still colored black. Also, the reaction hardly proceeds if any other kind of ether solvents is used.
Generally, diethyl ether is used as a solvent when preparing the Grignard reagent from fluoroaryl halide and magnesium. However, reaction heat produced in the reaction of bromopentafluorobenzene and magnesium is so large (89 Kcal/mol) that the reaction is not readily controlled. Particularly, diethyl ether involves a safety problem because it is a highly inflammable compound with a low boiling point.